Intercell interference reduction

Abstract

A distributed antenna system based wireless cellular communication system with transmit side linear interference cancellation is described. In this system the effective channel elements (I) and (II) are estimated and reported by mobile station MS1 and MS2, respectively, to a transmit weight matrix processing apparatus. Processing apparatus uses the effective complex channel matrix (one row reported by each mobile station) to differentially update the transmit weight matrix used for the transmit side linear interference cancellation.

The invention claimed is: 
     
       1. A method of downlink interference suppression for distributed antenna system based wireless cellular communication with transmit side linear interference cancellation, including the steps of
 determining, by a distributed antenna system based wireless communication system, effective complex channel matrix estimates; 
 differentially updating, by the distributed antenna system based wireless communication system, a complex transmit weight matrix in accordance with:
     W   (n+1)   =W   (n)   ΔW   (n+1)    
 
 
       where
 W (n+1)  is the updated complex transmit weight matrix, 
 W (n)  is the previous complex transmit weight matrix, and 
 ΔW (n+1)  is a differential update matrix, defined by
   Δ W   (n+1) =( E   (n) ) −1   Q  
 
 
 
       where
 E (n)  is an estimated effective complex channel matrix at least partially based on the determined estimates, and 
 Q is a predetermined desired link quality matrix. 
 
     
     
       2. A distributed antenna system based wireless cellular communication system with transmit side linear interference cancellation, including
 means adapted to determine effective complex channel matrix estimates; 
 means adapted to differentially update a complex transmit weight matrix in accordance with:
     W   (n+1)   =W   (n)   ΔW   (n+1)    
 
 
       where
 W (n+1)  is the updated complex transmit weight matrix, 
 W (n)  is the previous complex transmit weight matrix, and 
 ΔW (n+1)  is a differential update matrix, defined by
   Δ W   (n+1) =( E   (n) ) −1   Q  
 
 
 
       where
 E (n)  is an estimated effective complex channel matrix at least partially based on the determined estimates, and 
 Q is a predetermined desired link quality matrix. 
 
     
     
       3. The system of  claim 2 , wherein the means adapted to update the complex transmit weight matrix includes
 a matrix inverter inverting the estimated effective complex channel matrix E (n) ; 
 a differential update matrix forming unit connected to the matrix inverter for forming the differential update matrix ΔW (n+1) ; 
 a transmit weight matrix update unit connected to the differential update matrix forming unit for updating the complex transmit weight matrix. 
 
     
     
       4. A transmit weight matrix processing method for distributed antenna system based wireless cellular communication with transmit side linear interference cancellation, including the steps of
 determining, by an inverter, the inverse of an effective complex channel matrix from estimates of an effective complex channel matrix reported by mobile stations; 
 updating, by a differential update matrix forming unit, a differential update matrix based on the determined inverse of the effective complex channel matrix; 
 differentially updating, by a transmit weight matrix update unit, a complex transmit weight matrix in accordance with:
     W   (n+1)   =W   (n)   ΔW   (n+1)    
 
 
       where
 W (n+1)  is the updated complex transmit weight matrix, 
 W (n)  is the previous complex transmit weight matrix, and 
 ΔW (n+1)  is a differential update matrix, defined by
   Δ W   (n+1) =( E   (n) ) −1   Q  
 
 
 
       where
 E (n)  is an estimated effective complex channel matrix at least partially based on the determined estimates, and 
 Q is a predetermined desired link quality matrix. 
 
     
     
       5. A transmit weight matrix processing apparatus for a distributed antenna system based wireless cellular communication system with transmit side linear interference cancellation, including
 an inverter adapted to determine the inverse of an effective complex channel matrix from estimates of the effective complex channel matrix reported by mobile stations; 
 a differential update matrix forming unit adapted to update a differential update matrix based on the determined inverse of the effective complex channel matrix; 
 a transmit weight matrix update unit adapted to differentially update a complex transmit weight matrix in accordance with:
     W   (n+1)   =W   (n)   ΔW   (n+1)    
 
 
       where
 W (n+1)  is the updated complex transmit weight matrix, 
 W (n)  is the previous complex transmit weight matrix, and 
 ΔW (n+1)  is a differential update matrix, determined in the differential update matrix forming unit as
   Δ W   (n+1) =( E   (n) ) −1   Q  
 
 
 
       where
 E (n)  is an estimated effective complex channel matrix at least partially based on the determined estimates, and 
 Q is a predetermined desired link quality matrix.